The invention disclosed herein pertains to display devices such as are commonly known as neon signs. Such signs comprise glass tubes which are bent into various configurations and have electrodes sealed into their opposite ends. The color of the light which is emitted when a high electric potential is applied across the electrodes depends on the particular inert gas with which the tube is filled. Argon, Krypton and Neon are the most commonly used gases, but for the sake of brevity all such light emitting inert gas filled tubes will be called neon tubes herein.
Neon signs customarily comprise frames or panels on which the configured gas filled tube is supported by means of standoffs or insulating supports. Lead wires typically extend from the electrodes through the pinched-off ends of the glass tube and insulated wires which extend from a high voltage power supply are directly connected to the electrode wires and the connections are wrapped with insulating tape or a heat-shrinkable insulating tube. Fine gauge supply wire is used because the current through a neon tube is relatively small, in the milliampere range, but the power supplies have high output voltage. Voltages may range from about 6000 volts to 15,000 volts which, needless to say, produces trauma when voltages at that level are accidentally applied to the human body. The lead wires from the power supply to the neon tube are usually covered with a very flexible insulating material such as rubber having a wall thickness of about 1.5 mm. These signs are often positioned in rather hostile environments which can result in degradation of the wire insulation and unintended contact of the wire by persons.
As a result of the possible hazard of neon signs and the insulating systems that have been proposed for them, no safety organization such as Underwriters Laboratories, Inc. has ever, insofar as applicants are aware, allowed a neon sign design of any manufacturer to carry its certification mark.